Fuel feed control system responsive to flame color



B. D. ALEXANDER ET AL 3,304,989

2 Sheets-Sheet 1 FUEL FEED CONTROL SYSTEM RESPONSIVE -TO FLAME COLOR IATTORN EY INVENTORS Bernard D. Alexander BY Melvin J. Zuc ker K 53 kenNkNN A Feb. 21, 1967 Filed Nov 19, 1964 Feb. 21, 1967 D. ALEXANDER.

FUEL FEED CONTROL SYSTEM RESPONSIVE TO FLAME COLOR 2 Sheets-Sheet 2Filed Nov. 19, 1964 m8 J W g E m 3:50 wow 52 INVENTORS Bernard D.Alexander Melvin J. Zucker BY ATTORN EY United States Patent O 3,304,989FUEL FEED CONTROL SYSTEM RESPONSIVE T FLAME COLOR Bernard D. Alexander,Clark, and Melvin J. Zucker, Somerville, N.J., assignors to AmericanRadiator & Standard Sanitary Corporation, New York, N.Y., a corporationof Delaware Filed Nov. 19, 1964, Ser. No. 412,413 1 Claim. (Cl. 158-125)This invention pertains to systems for controlling the I feeding of fuelto a fuel burner and more particularly to such systems which control thefeeding of fuel to a burner in accordance with the presence of fuelcombustion in the burner.

In many remote control fuel burning systems, fuel is supplied to aburner in response to a remotely generated signal. At the same time, orshortly thereafter, the fuel as it leaves the burner is ignited.Generally, there is no human supervision of the operation. Accordingly,if ignition does not take place then at best fuel is wasted. However, ifthe fuel is a volatile gas then there is the very serious hazard ofaccumulation of the gas and the danger of explosion. Systems have beenproposed which shut oif the flow of fuel if combustion is not attained.Nevertheless, with such proposed systems there is the possibility thatsometime after combustion has been attained the flame goes out.Accordingly, every reliable system must include means for continuouslymonitoring the flame.

Heretofore, the flame was indirectly monitored. More specifically, theheretofore available gas flame sensors employed heat sensors such asthermocouples or ionized gas detectors. In general, a thermocouple isplaced near or in the flame. The thermocouple generates an electromotiveforce which is functionally related to the temperature of thethermocouple junction. The electromotive force so generated is used tocontrol the flow of fuel to the burner. It should benoted, however, thatthe thermocouples do not instantaneously respond to the presence orabsence of a flame since there is a thermal lag due both to thethermocouple and the ability of its mechanical supporting structure todissipate heat. Ionized gas detectors on the other hand depend on theconductivity of a hot ionized gas to provide an electrical current pathto a device which controls the flow of fuel to a burner. Such detectorsare delicate and have critical operating characteristics.

' It is, accordingly, a general object of the invention to provide animproved system for controlling the flow of fuel to a fuel burner.

It is another object of the invention to provide an improved fuel feedsystem whose sensing element can be placed outside the high heat regionof the fuel burner and, accordingly, has a longer lifetime.

It is a further object of the invention to provide an improved fuel feedsystem which is, on the one hand, rugged and reliable and, on the otherhand, relatively inexpensive.

Broadly, the invention contemplates a fuel feed system to be used incombination with apparatus that feeds fuel to a burner via a valve meansto a fuel burner. The system includes means for actuating the valvemeans for a given period of time during which only a given quanf tity offuel is fed to the burner. During this time, the flame should be struck.Photoelectric means are provided for sensing illumination from the flameof burning fuel. If the photoelectric means senses such illumination,third means are activated which insure continued actuation of the valvemeans as long as the photoelectric means senses illumination from theflame.

In a gas burning system the optimum utilization of fuel is obtained whenthe flame is blue, that is, when the 3,304,989 Patented Feb. 21, 1967ice proper proportion of gas and oxygen are consumed in the burner. Ifthe flame is over rich in fuel then the flame is more luminous since itis more yellow than blue. Accordingly, even though the flame isgenerating heat the system is operating inefiiciently. It should beapparent that the above mentioned thermocouples and hot ionized gasdetectors cannot detect such an inefficiently operating fuel burner.

It is, accordingly, another object of the invention to provide a fuelcontrol system which by employing a single flame sensor not onlycontrols the flow of fuel to a burner in accordance with the presence orabsence of a flame but also in accordance with the operating efficiencyof the fuel burner.

This aspect of the invention contemplates that the photoelectric meansgenerate a current as long as the flame is present and that this currentactivates means for insuring the continued actuation of the valve means.However, the photoelectric means generates a current related to theintensity of the sensed illumination. Therefore, if the flame becomesmore luminous due to a yellow component, the current increases. Furthermeans are provided which are activated when the current exceeds apredetermined magnitude to deactuate the valve means.

According to a feature of the invention, means are also provided so thatif the means which first a-ctuates the valve means to supply the initialquantity of fuel operates beyond a given period of time the valve meansis deactuated whether or not a flame is sensed.

Finally, it should be noted that in many remote control heating systemsthermostats or similar switching means are employed which create thedemand for fuel burning. When such a switching means is incorporated inthe heretofore described fuel feed control system it is possible thateach time the valve means is deactuated for any malfunctioning of thecontrol system, the switching means may attempt to restart the cycle ofoperation. In such a case there could be an incremental accumulation ofuncombusted fuel which is as hazardous as a continuous accumulation.

Therefore, according to another feature of the invention there isprovided means for de-energizin'g the photoelectric means and the meanswhich initially actuates the valve means whenever the valve means isdeactuated while the switching means demands the burning of fuel.

Other objects, features and advantages of the invention will be apparentfrom the following detailed description when read with the accompanyingdrawings which show, by way of example, and not limitation, apparatusfor practicing the invention.

In the drawings:

FIG. 1 is a schematic diagram of a first embodiment of the invention;and

' FIG. 2 is a schematic diagram of another embodiment of the invention.

Referring to FIG. 1' there is shown a fuel feed control system 10wherein a fuel such as a gaseous hydrocarbon is fed from a fuel source(not shown) via a solenoidoperated valve 12 to burner 14 where it isignited by a conventional ignition system 16 to produce a flame 18.

. The remainder of FIG. 1 is concerned with a control system foractuating solenoid-operated valve 12 and centers around thephotoelectric means 20, the timing relay 22, the blue flame relay 24,the yellow flame relay 26, the time-delay relay 28, the latching relay30, the rectifier 32, and the demand means 34.

It should be noted that the system 10 as presently shown depicts allrelays in their normal or deactivated state and with thesolenoid-operated valve 12 deactuated. Accordingly, at this time flame18 should not be present. However, it is shown in dotted lines merely toindicate its functional relationship with photoelectric means 20.

Before describing the operation of system 10, various components andreference character convention will be explained.

Photoelectric means 20 includes the cadmium sulfide cell 20C and theoptical system 20L which enhances the sensitivity of cell 20C. Thecadmium sulfide cell 20C is a photoconductive solid state element whoseelectrical resistance decreases with increasing illumination falling onits active surface. Accordingly, the cell 20C is shown as a variableresistor. The response curve of the cadmium sulfide cell 20C peaks verysharply in the blue-green region of the visible spectrum and falls offvery sharply in the infra-red region. Therefore, cell 20C is insensitiveto the heated walls which usually surround the burner.

Timing relay 22, the means for actuating solenoidoperated valve 12 foronly a given period of time, includes: a coil 22L, a timing capacitor22C connected to one end of coil 22L, and three contact sets 22K1, 22K2,and 22K3. Contact set 22K1 includes: the normallyopen fixed contact22K10 and the moving contact 22K1m. Contact set 22K2 includes: thenormally-open fixed contact 22K20, the normally-closed fixed contact22K2c, and the moving contact 22K2m. Contact set 22K3 includes: thenormally-open fixed contact 22K3oand the moving contact 22K3m.

Blue flame relay 24, the means for continuing the actuation ofsolenoid-operated valve 12 as long as illumination from the flame issensed, includes the coil 24L and the contact set 24K with thenormally-open fixed contact 24Kc, the normally-closed fixed contact 24Kcand the moving contact 24Km. It should be noted that the coil 24L ofrelay 24 is connected to cell 20C so that when cell 20C conducts andpasses current, this current passes through coil 24L as will hereafterbecome apparent. Yellow flame relay 26, a means for deactuatingsolenoidoperated valve 12 when the current passed by cell 20C exceeds agiven magnitude include a coil 26L having a sensitivity less than thesensitivity of coil 24L and a contact set 26K with a normally-open fixedcontact 26K0, a normally-closed fixed contact 26Kc and a moving contact2-6Km. It should be noted that coil 26L is in series with coil 24L sothat current passed by cell 20C also passed through coil 26L. It shouldalso be noted that the sensitivities of coils 24L and 26L can be sochosen to be sensitive to diflerent ranges of currents generated by cell20C in response to different color flames or different ranges of colors.

Time-delay relay 28, a means for deactuating solenoidoperated valve 12if timing relay 22 is energized beyond a given period of time, is aconventional time-delay relay which operates only after its coil 28Lreceives current continuously for a given period of time and includesthe contact set 28K with the normally-open fixed contact 28K0 and themoving contact 28Km.

Latching relay 30, a means for latchingly interrupting energization ofcell 20C and timing relay 22, is a conventional latching relay that isalternately energized and deenergized as its coil 30L receivessequential pulses of current. Relay 30 includes the contact set 30K witha normally-closed fixed contact 30Kc and moving contact 30Km. One end ofcoil 30L is connected to contact sets of relays 24 and 26 in parallel.Also, connected, in parallel with said contact sets, to said end of coil30L is manually-operable normally-open switch 30s. Connected to theother end of coil 30L is current limiting resistor 30R. Relay 30operates slower than relay 24.

Relays 22, 24 and 26 are D.C. operated and relays 28 and 30 are A.C.operated.

It should be noted that all the relays are shown in their normal orde-energized states. When any relay is energized its moving contactmoves toward its coil, breaking contact with the normally-closed fixedcontacts of the sets and making contact with the associatednormally-open contacts of the sets.

Rectifier 32 includes diode 32D whose anode is connected to contact set30K of latching relay 30 and whose cathode is connected to the filternetwork of resistor 32R and 32C in parallel. Demand means 34 includesA.C. source 34A and switch 348. Although switch 348 is shown as amanually operable switch it could also be a thermostat switch.

The normal operation of the system will now be described.

Whenever there is a demand for the burning of fuel, switch 345 is closedand remains closed until the demand no longer exists. Alternatingcurrent passes via switch 345, contact 30K and line 35 and is rectifiedto a direct current by rectifier 32. The direct current is fed via line36 to energize cell 20C by applying a DC. voltage to its upper terminal.Charging current flows through capacitor 22C and coil 22L to return line38 until capacitor 22C is charged to the DC. voltage on line 36. Whilethe charging current flows, relay 22 is energized. The period of timecharging current flows is determined primarily by the capacitance ofcapacitor 22C and the resistance in coil 22L. While relay 22 isenergized the alternating current on line 40 passes via contacts 22K2mand 22K20 of set 22K2 and line 42 to solenoid-operated valve 12.Solenoidoperated valve 12 is actuated and fuel flows to burner 14. Atthe same time, contact set 22K3 closes, energizing ignition system 16which ignites the fuel flowing from burner 14 causing the striking offlame 18, which will be assumed as blue for the time being. Cell 20Cstarts conducting and direct current flows from line 36 via cell 20C andcoils 24L and 26L to return line 38. Because of the amount ofillumination from the blue flame the magnitude of the direct currentflow is only suflicient to activate relay 24.

When capacitor 22C is fully charged after a given period of time, relay22 automatically deactivates. The alternating current on line 40 nowflows via contacts 22K2m and 22K2c, line 44, contacts 24Km and 24K0,line 46, and contacts 26Km and 26Kc to line 42 to continue the actuationof solenoid-operated valve 12. Fuel will, accordingly, be fed to burner14 as long as a blue flame is present and until switch 348 is opened.The opening of switch 348 interrupts the flow of alternating current online 48 and, consequently, on lines 40 and 42 deactuatingsolenoid-operated valve 12 and terminating fuel flow to burner 14. Atthe same time, direct current ceases on line 36. Current no longer flowsthrough cell 20C and relay 24 is deactivated. Capacitor 22C alsodischarges.

The abnormal operations will now be described. These abnormal operationsare: (1) no flame is struck or the flame goes out; (2) the flame that isstruck is yellow or changes'from blue to yellow; (3) relay 22 operatesfor longer than the predetermined period of time; (4) cell 20C is opencircuited; (5) cell 20C is short circuited; (6) direct current fails;and (7) alternating current fails.

Consider case 1. It will be recalled that when relay 22, after bein-gactivated and then automatically deactivated after the given period oftime, fed alternating current on line 44 to contact 24Km. Anytime relay24 is not activated contact 24 K172 is connected to contact 24Kc and thecurrent passes via line 50 to latching relay 30 which is activatedcausing contact set 30K to open. The opening of contact set 30K isequivalent to opening switch 348 and the system turns itself oil. Itshould be noted that relay 24 will be deactivated when no current flowsthrough coil 24. This can occur if no flame appears or the flame goesout (case 1); cell 20C is open circuited (case 4); direct current failsafter the flame is struck (case 6).

Consider Case 2. Whenever the flame 18 is yellow, cell 20C conductsheavily as hereinabove described. Ac-

' cordingly, sufiicient current flows to activate relay 26 in additionto relay 24. Contact 26Km transfers from contact 26'Kc to contact 26K0of relay 26 and the alternating current on line 46 is transferred fromline 42 to line 50.

Solenoid-operated valve 12 is deactuated and relay 30 is activated.System shuts itself down as previously described for case 1. It shouldbe noted that heavy current flow through coil 26 can also occur if cell20C is short circuited (case 5).

Consider now case 3. When relay 22 is initially activated, in additionto the previously described phenomena, contact set 22K1 closes andalternating current flows via line 40, contact set 22K1 and line 52through the coil 28L of time delay relay 28 to return line 38. If, forexample, the period of time of activation of relay 22 is three secondsand time delay relay 28 is chosen so that it is activated only if coil28L receives current for five seconds, then if relay 22 remainsactivated for any reason more than five seconds, relay 28 is activated.Contact set 28K closes. The alternating current on line 52 passes viacontact set 28K and line 54 to coil 30L. Relay 39' is activated andcontact set 30K opens. Then the system shuts itself down.

Consider now the situation in case 6 when direct current is neveravailable on line 36. Accordingly, when switch 343 is closed relay 22 isnot activated and cell 20C not energized. Accordingly, the alternatingcurrent from switch 348 flows via contact set 30K, line 40, contact set22K2, line 44, contact set 24K and line 50* to coil 35L. Contact set 30Kopens and the system shuts itself down in the usual manner.

In case 7, the failure of alternating-current is equivalent to thenormal opening of switch 348.

It should be noted that except for the failure of alternating currenteach abnormal operation entailed the activation of latching relay 30.Relay 30 is purposely chosen to be a latching relay requiring a manualresetting to draw a users attention to the abnormal operation of thesystem. Resetting is accomplished merely by momentarily closingspring-return push button switch 308 causing a pulse of alternatingcurrent to fiow via line 48, switch 308 and line 50 to coil 30L. Thispulse, following a pulse which activated relay 30, deactivates relay 30causing contact set 311K to close and returns the system to its normalstate.

Referring now to FIG. 2, there is shown a fuel feed control system 110wherein a fuel such as a gaseous hydrocarbon is fed from a fuel source(not shown) via a solenoid-operated valve 112 to burner 114 where it isignited by a conventional ignition system 116 to produce a flame 118.

The remainder of FIG. 2 is concerned with a control system for actuatingsolenoid-operated valve 112 and centers around the photoelectric means121 the timing means 122, the blue flame relay 124, the yellow flamerelay 126, the power supply 130 and the demand means 134.

It should be noted that the control system 110, as presently shown,depicts all relays in their normal or deactivated state and with thesolenoid-operated valve 112 deactuated. Accordingly, at this time, flame118 should not be present. However, it is shown, in dotted lines, merelyto indicate its functional relationship with photoelectric means 120.

Before describing the operation of control system 1111, variouscomponents and reference character conventions will be explained.

Photoelectric means 120' includes the cadmium sulfide cell 120C and theoptional system 120'L which enhances the sensitivity of cell 120C. Thecadmium sulfide cell 120C is a photoconductive solid state element whoseelectrical resistance decreases with increasing illumination falling onits active surface. Accordingly, the cell 120C is shown as a variableresistor. The response curve of the cadmium sulfide cell 120C peaks verysharply in the blue-green region of the visible spectrum and falls offvery sharply in the infra-red region. Therefore, cell 1200 isinsensitive to the heated walls which usually surround the burner.

Timing means 122, the means for actuating solenoidoperated valve 112 isthe circuit breaker CB. The relay 123 and the current limtiing resistor125 are serially connected in that order to circuit breaker CB. Thecircuit breaker CB includes a contact set CBK and a 'bimetal elementCBL. Current flowing through circuit breaker CB heats the element CBLand is adjusted so that the circuit breaker CB operates in approximatelyfour seconds. Relay 123 includes a coil 123L and a contact set 123Khaving a normally-open fixed contact 123K0 and a moving contact 123Km.

Blue flame relay 124, the means for continuing the actuation ofsolenoid-operated valve 112 as long as illumination from the flame issensed, includes the coil 124L and the contact set 125K with thenormally-open fixed contact 124K0, the normally-closed fixed contact124Kc and the moving contact 124Km. It should be noted that the coil124L of relay 124 is connected to cell 120C so that when cell 120Cconducts and passes current, this current passes through coil 124L aswill hereafter become apparent. Yellow flame relay 126, a means fordeactuating solenoid-operated valve 112 when the current passed by cell120C exceeds a given magnitude includes a coil 126L having a sensitivityless than the sensitivity of coil 124L and a contact set 126K with anormally-closed fixed contact 126Kc and a moving contact 126K111. Itshould be noted that coil 126L is in series with coil 124L so thatcurrent passed by cell 120C also passed through coil 126L. It shouldalso be noted that the sensitivities of coils 124L and 126L can be sochosen to be sensitive to different ranges of currents generated by cell120C in response to diiferent color flames or different ranges ofcolors.

The power sup-ply 130 includes an alternating current source 131 whichcan vary from to 130 volts AC. The alternating current source 131 isconnected to DC. power supply 128 via transformer T1. Transformer T1 ispreferably a saturable transformer which provides a near constantvoltage output. Capacitor 132 limits the current fed to transformer T1.DC. power supply 128 preferably includes a full wave rectifier includinga choke-capacitor filter, and a bleeder resistor. Source 131 also feedstransformer T2 to supply current for valve 112 under control of relay123, as will hereinafter become apparent.

The demand means 134 is a switch which for simplicity 1s shown asmanually operable but can be a thermostat switch.

Relays 123, 124 and 126 are D.C. operated and are shown in their normalor deenergized states. When any relay is energized its moving contactmoves toward its coil, breaking contact with the normally-closed fixedcontacts of the sets and making contact with the associatednormally-open contacts of the sets.

The normal operation of the system will now be described.

When there is a need for more heat switch 134 closes. Current flowstherethrough and simultaneously through three circuits: (1) via contactset CBK, element CBL, coil 123L and resistor 125 to return bus 129; (2)via contact set CBK, bus 140, bus 141, contacts 124Km and 124Kc, bus 142and ignition system 116 to return bus 129; and (3) via contact set CBK,bus 140, bus 143, cell C, coil 124L, and coil 126L to return bus 129.

The current through coil 123L energizes relay 123 causing the closing ofcont-act set 123K which results in the feeding of alternating currentfrom transformer T2 to solenoid-operated valve 112. Fuel starts flowingfrom the source (not shown) to burner 114.

Since there is no flame 118, the resistance of cell 120C limits thecurrent through coil 124L below the value required to energize relay124. Accordingly, the ignition system 116 is actuated to ignite the fuelflowing from burner 114. As will hereinafter become apparent, a foursecond time period is allowed initially as a trial for ignition. Undernormal circumstances, the fuel will ignite well before the end of thetime period. When the cell 124C senses a blue flame, relay 124 isenergized and moving contact 124K111 transfers from contact 124Kc tocontact 124K0. Ignition system 116 is deactuated and a shunting patharound element CBL is established. In particular, current now flows fromcontact set CBK via busses 140 and 141, contacts 124Km and 124K0, bus145, contacts 126Kc and 126K111 to bus 146. Therefore, little or nocurrent flows through element CBL which stops heating.

Fuel is now fed to burner 114 until either switch 134 is opened, or theflame 118 goes out; or the color of flame 118 changes from blue toyellow. Each situation will be discussed.

When switch 134 is opened, no more current is fed to relay 123 and relay124, and both de-energize. The deenergization of relay 123 interruptsthe flow of current to solenoid-operated valve 112 stopping the flow offuel. The de-energization of relay 124 returns it to its rest state andthe system 110 is ready for reactivation.

If the blue flame 118 goes out, the current through relay 124 markedlydecreases causing relay 124 to de-energize. The connection betweencontacts 124K0 and 124K111 opens breaking the shunt path around elementCBL. Element CBL starts heating and in four seconds contact set CBKopens. The opening of contact set CBK has the same eflect as the openingof switch 134.

When the flame 118 changes from blue to yellow, cell 120C conducts morecurrent and relay 126 is energized. Contact set 126K opens and the shuntpath around element CBL opens. Element CBL starts heating and after fourseconds contact set CBK opens.

If a flame were never struck, then relay 124 would not energize and noshunt path would be established around element CBL. Accordingly, afterfour seconds contact set CBK would open.

Thus it is seen in every case of abnormal operation a timing element isallowed to operate so that after a predetermined period of time themeans which control the flow of fuel to the burner are deactuated.

There has, accordingly, been shown and described a reliable fuel feedsystem which includes a photoelectric means to monitor the presence of aflame. The photoelectric means also permits the control of the flow offuel in accordance with the color of the flame. Furthermore, by theincorporation of a latching means for interrupting current flow there isno chance of the system recycling after malfunctioning without theintervention of a human being.

While only two embodiments of the invention have been shown anddescribed in detail there will now be obvious to those skilled in theart many modifications and variations thereof which satisfy the objectsof the invention without departing from the spirit thereof as defined inthe appended claim.

What is claimed is:

A fuel feed control system for use with apparatus for burning fuel fedto a fuel burner via a valve means, and including ignition means forigniting fuel at said fuel burner, said control system furthercomprising: a source of electric current including fist and secondterminals; circuit breaker means including a contact set having a firstterminal connected to the first terminal of said source of electriccurrent and a second terminal, the terminals of said contact set beingnormally connected to each other, and a heating element means includinga first terminal connected to said contact set and a second terminal,said heating element means causing the terminals of said contact set todisconnect when electric current has passed through said heating elementmeans for a given period of time; a first relay including a windingconnected between the second terminals of said heating element means andsaid source of electric current and a contact set means for controllingthe actuation of said valve means; a photo conductive means for sensingthe color of the flame of burning fuel and having a conductivity whichincreases as the color of the flame changes from blue to yellow, saidphotoconductive means including a first terminal connected to the secondterminal of the contact set of said circuit breaker means and a secondterminal; a second relay including a winding having a first terminalconnected to the second terminal of said photoconductive means and asecond terminal, a contact set including a t normally-closed contact, anormally-open contact and a transfer contact, said transfer contactbeing positioned against said normally-closed contact when an electriccurrent less than a first given value passes through the winding of saidsecond relay and being positioned against said normally-open contactwhen an electric current greater than said first given value passesthrough said winding; means for connecting the normally-closed contactof said relay to the second terminal of said circuit breaker means,means for connecting the normally-closed contact of said second relay tosaid ignition means; and a third relay including a winding connectedbetween the second terminal of the winding of said second relay and thesecond terminal of said source of electric current and a contact setincluding a first terminal connected to said normallyopen contact of thecontact set of said second relay and a second terminal connected to thesecond terminal of said heating element means, said terminals of saidcontact set being connected to each other as long as a current less thana second given value greater than said first given value passes throughsaid winding.

References Cited by the Examiner UNITED STATES PATENTS 2,673,603 3/1954Outterson 158-28 2,695,054 11/1954 Millerwise et al. 158-28 2,695,66111/1954 Porter 158125 X 2,911,540 11/1959 Powers.

2,958,811 11/ 1960 Mungaard.

2,966,619 12/1960 Burckhardt 15828 X 3,049,169 8/1962 Bredesen et al.158125 X 3,080,708 3/1963 Carr 15828 X 3,088,516 5/1963 Marcellino etal. 158128 X 3,143,161 8/1964 Graves et al. 158-28 FREDERICK KETTERER,Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N00 3,304,989 February 21 1967 Bernard De Alexander et ale It is hereby certifiedthat error appears in the above numbered patent requiring correction andthat the said Letters Patent should read as corrected below.

Column 8, line 2, for "fist" read first line 16,

after "sensing insert for column 8, line 33, beginning with "relay to"strike out all to and including "of said" in line 34, same column 80Signed and sealed this 28th day of November 19670 (SEAL) Attest:

EDWARD J BRENNER Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer

